1. Field of the Invention
The present invention relates to a method for the production of a high strength electric seam welded oil-well pipe.
2. Description of the Prior Art
With the increasing depths being drilled for oil and gas, there is increasing demand for high strength oil-well pipe. This demand is barely satisfied by the use of high strength pipe obtained in the form of seamless pipe which has been subjected to quenching and tempering.
However, more recently, high strength oil-well pipe has been manufactured by a method which comprises subjecting electric seam welded pipe to quenching and tempering. Such electric seam welded pipe is more inexpensive than seamless pipe, but has certain demerits, as follows:
(1) The finer grain produced by controlled rolling and controlled cooling, an advantage of electric seam welded pipe, cannot be fully utilized.
(2) Such strengthening precipitation type elements as Nb, V or Ti, another advantage of electric seam welded pipe, cannot be utilized.
(3) Because the dimensional precision, another advantage of electric seam welded pipe, is adversely affected by quenching, straightening and leveling is required.
Thus, a disadvantage of the prior art is that the production of the high strength oil-well pipe by subjecting electric seam welded pipe to quenching and tempering cancels out all the inherent advantages of electric seam welded pipe.